We wish to elucidate the relationship between CNS mechanisms of reward and drugs of high abuse. This objective has several sub-themes: the understanding of acute vs. chronic effects, the understanding of effects of withdrawal and abstinence, and the significance of tolerance effects to drugs of abuse. Our secondary objective is to better understand the behavioral significance of CNS mechanisms of reward. The major way of our studying this topic is to perform intracranial self-stimulation (ICSS) experiments, and to study the effects of drugs of abuse (specifically amphetamine and narcotics) on CNS mechanisms of reward as measured by self-stimulation. It is our view that not only are the ICSS techniques useful in assessing pharmacological interventions, but they can provide inroads into the basic mechanisms of reward which we believe are central to the unifying property of drugs of abuse; that they alter one or more mechanisms of reinforcement, the net effect of which is to enhance reward. We have already performed a variety of experiments looking at the effects of amphetamine and morphine on different neuroanatomical sites that support ICSS.